3 Answers
3

the subject, when it is slightly more on one side. Of course, in some photos, putting the subject in the corner is done to achieve an artistic effect, but I'm not talking about those cases.

the scene, for example when the horizon is too low or too high.

Remove:

the elements which attract attention away from the subject of an image. For example, if it is an image of a person in a street, and there are no other people except someone not very nice to see in the corner, it's better to crop the image.

the unwanted elements. For example, if there is a tree outside of the picture, but you see a part of this tree in a corner, there is a good reason to crop the image.

the elements that show that the photo is not straight. For example, a tall building on a side of the photo can attract attention by the fact that it "falls" to the center of an image, due to perspective problems. Another example is anything straight in real life, which is shown as a curve on a photo, due to the lens distortion.

the empty areas, except when those areas add an artistic value. A block of brick wall is an empty area in this case.

To resume, I crop photos when either there are elements which must not be here or when there is nothing interesting on the sides of the image.

In the sample photo, it's difficult to tell what was your purpose. If the subject is a young girl watching through a window, I'll probably crop everything except the girl's head, thus keeping a small margin around to show the snow outside and the black frame of the window.

A huge factor you should consider is how many print sizes will you end up making from the images. If you decide on a single size, go ahead and crop the images exactly how you want using that ratio.

If you are planning to print the images to various sizes, consider the aspect ratio of each size. It may be better to crop the images at the time you print so that each print size has enough image to work with.

I see folks crop tight either while shooting or after the fact for artistic reasons. What they fail to consider is that what looks good on a 4x6 may not work on an 8x10 due to the difference in cropping.

Using your example above, for an 8x10 you would likely loose part of the top or bottom of the image. Would you use the center, or crop out the dark area at the bottom? The dark area to me artistically lends to the dreariness of the kid looking outside at the snow wanting to play. If you crop out the shadows, it makes it a more lighter image and conveys happiness to me. It boils down to what you want to convey, and what you are willing to give up on the printed image.

Usually, when cropping a photo, be it for print or other uses (like my blog), I look at a few things in the picture. Sometimes the picture contains unwanted elements; things I didn't notice when taking the picture, or, because my viewfinder only has a 95% coverage, things end up in the picture at the edges just because I couldn't see them.

For me, cropping is about achieving an artistic effect (very narrow or tall photos for instance) or just about removing unwanted elements. Looking at the picture above, I'd probably try to get rid of the thermometer at the top. Or maybe not, since the space at the top of the image is what gives it 'air'.

In the end, I guess, it just depends on what you want to do with the image.